31 Vestibular Neurectomy – Translabyrinthine Approach
Henning Hildmann
Indications
Vestibular vertigo and unserviceable hearing, temporal bone fractures with injuries of the facial nerve
Contraindications
Infections of the mastoid and the middle ear
Surgical Steps
1. Extended mastoidectomy is performed. The sinus, media and posterior fossa are identified under a thin layer of bone as well as the body of the incus and the semicircular canals (Fig. 31.1). The nerve is identified in its mastoidal portion using a drill larger than the diameter of the nerve and drilling in the direction of the course of the nerve. A thin cover of bone protects the nerve from injury during the following steps. Before opening the internal auditory canal a good exposure of the surgical site is impor- tant. It should be larger than for a labyrinthectomy. The infra-, supra- and retrolabyrinthine cells are removed to model the semicircular canals to identify the landmarks for the next steps. The cavity is drilled downwards.
The jugular bulb, which is very variable in height, may be reached. Gener- ally it is more anteriorly situated. Its exposure is not mandatory as in tumour surgery. The cochlear aqueduct, which lies frontally above the jugular bulb, should be respected. The glossopharyngeal nerve exits the posterior cranial fossa immediately underneath and may be injured. If the sinus is protruding, the covering bone may be thinned and fractured backwards. After removal of the incus and if possible the head of the mal- leus the facial recess is opened and the facial nerve can be seen above the oval window. This helps to control the course of the nerve (Fig. 31.2). In a well-pneumatized temporal bone it can be followed to the cochleariform process.
2. The lateral semicircular canal is opened followed by opening of the poste- rior and superior semicircular canals. They should not be drilled away completely at this stage because they serve as landmarks. The ampulla of the superior canal protects the facial nerve (Fig. 31.3).
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Fig. 31.1
Fig. 31.3
Fig. 31.2
Fig. 31.4
3. The subarcuate artery is identified, bleeding may be controlled with a slowly revolving diamond drill or bipolar coagulation, and the lateral canal is removed. The vestibule is opened. After removal of the posterior canal the endolymphatic duct leading from the vestibule to the endolymphatic sac can be seen. There is a risk of the shaft of the drill contacting the facial nerve and causing heat damage (Fig. 31.4). After removing the bone over the lat- eral and superior ampulla superiorly and the ampulla of the posterior canal
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inferiorly, the nerve ends of the superior and lateral ampullary branch can be seen superiorly and the singular nerve (to the posterior ampulla) inferi- orly. The nerves outline the upper and lower limits of the internal auditory canal. The upper vestibular nerve is located lateral to the facial nerve and protects the nerve from injury in this region.
4. While the fundus of the internal auditory canal is located immediately under the vestibulum, its porus to the posterior fossa is about 1 cm more medial under hard bone. The exposure requires patient drilling. The dura of the internal auditory canal should not be opened to protect the nerves. The bone above and below the canal is removed generously downwards to the jugular bulb and upwards to the bone covering the dura of the middle fossa.
The canal remains covered with a thin layer of bone and is exposed in about half of its circumference, about 180 degrees, before removing the remaining bone and opening the dura because after opening the escaping cerebrospi- nal fluid may push the facial nerve into the operation field and the revolving drill. Drilling may become dangerous. Towards the posterior fossa the dura may be exposed. However, wide exposure as in acoustic neuroma surgery is not necessary. The bone covering the dura of the canal is lifted off with a curette (Fig. 31.5).
5. The dura is incised and the nerves are seen. The vertical crest separates the facial nerve from the vestibular nerves (Fig. 31.6). The VIIth nerve must be identified before proceeding. If identification is difficult the bone covering the nerve in its labyrinthine portion may be carefully thinned. A nerve monitor should be used. Towards the fundus the end of the internal audi- tory canal and the transverse crest are identified. The vertical crest sepa- rates the vestibular nerves. The posterior ampullary nerve, part of the infe- rior vestibular nerve, is found inferior to the crest (Fig. 31.7).
6. After clear identification the nerves are cut towards the fundus and are sep- arated with a hook (Fig. 31.8).
7. The internal auditory canal is closed with fascia and covered with abdomi- nal fat. Fibrin glue is used.
160 31 Vestibular Neurectomy – Translabyrinthine Approach
Fig. 31.5 Fig. 31.6
Fig. 31.7 Fig. 31.8
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